Obrussena bracteata (Iredale, 1925)

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 600-601

Obrussena bracteata (Iredale, 1925)

Figs 4F-I, 5

Obrussa bracteata Iredale, 1925: 269 , pl. 42, fig. 15.

Synonym:

Obrussena moeshimaensis Habe, 1952 a: 71-72, text fig. 6.

TYPE MATERIAL. — Not examined .

TYPE LOCALITY. — Off Narrabeen , New South Wales, Australia, 137-146 m, and 20 miles east of Babel Island, Tasmania, Australia, 119 m.

MATERIAL EXAMINED. — North of New Caledonia. BATHUS 4 : Loyalty Ridge. MUSORSTOM 6: stn DW 406 , 20°41’S, 167°07’E, stn DW 914 , Grand Passage, 18°49’S, 163°15’E, 600-616 m, 1 dd. 373 m, 1 dd .

New Caledonia proper. BIOCAL: stn DW33 , 23°10’S, 167°10’E , Vanuatu. MUSORSTOM 8: stn DW 976 , 19°25’S, 169°27’E, 160- 675- 680 m, 1 dd . — BATHUS 1 : stn DW 654 , Passe de Canala , 182 m, 1 dd .

21°17’S, 165°57’E, 237-298 m, 1 dd; stn DW 688, Passe de Wallis Island. MUSORSTOM 7: stn DW 604, 13°21’S, 176°08’W, Hienghu, 20°33’S, 165°00’E, 270-282 m, 1 dd; stn CP 701, Pas- 415-420 m, 1 dd.

se de Cap Baye, 20°58’S, 165°36’E, 302-335 m, 1 dd; stn DE Tonga. BORDAU 2 : stn DW 1548 , S of Nomuka Islands , 20°38’S, 705, 21°02’S, 165°38’E, 350-400 m, 1 dd. 175°03’W, 476-478 m, 1 dd; stn DW 1549 , 20°38’S, 175°00’W, Norfolk Ridge. BATHUS 3 : stn DW 824 , Banc Jumeau Ouest, 500 m, 1 dd; stn DW 1552 , 20°38’S, 174°58’W, 491-500 m, 1 23°19’S, 168°00’E, 601-608 m, 1 dd . — BERYX 11 : stn DW dd (Figs 4F-H); stn DW 1554 , 20°38’S, 174°58’W, 482-498 m, 2 10, 24°53’S, 168°21’E, 565-600 m, 2 dd; stn DW 35 , 23°33’S, lv, one of them destroyed to dissect the radula (Fig. 4I); stn DW 167°16’E, 550-570, 3 dd. 1615, Seamount, 23°03’S, 175°53’W, 482-504 m, 1 dd .

DISTRIBUTION. — Originally described from off the coast of Narrabeen and Babel Island , New South Wales, southeastern Australia, in 119-146 m. Subsequently cited from the Pleistocene of Moeshima , Japan (Habe 1952a), and the Japan and China Seas, in 50-200 m (Lin and Qi 1983; Hori 2000a). Records herein from New Caledonia, Tonga, Vanuatu and Wallis and Futuna (Fig. 5), in 182-675 m, live in 482-498 m.

DESCRIPTION. — Shell morphology. Length 9 mm, width 6 mm (largest specimen examined). Shell solid, short, oval (Fig. 4F). Body whorl large; spire conical, variable in length, with 1-4 whorls depending on the size of the animal. Larger specimens have more whorls than smaller specimens. Suture narrowly channeled. Protoconch globose, about 1.5 whorls and 800 Μm in diameter (Fig. 4G). Umbilicus wide and deep. Aperture wide and short, about 3/4 of the body whorl. Columellar margin simple, with no denticles. Sculpture of a number of punctuated spiral grooves (Fig. 4H). The punctuations are large, oval, and partially fused to the next one within each groove. The grooves are separated by gaps about as wide as the grooves themselves. Colour uniformly whitish. Operculum thin, covering the entire aperture.

Anatomy. The radular formula is 45 x 15.0. 15 in a specimen from Tonga ( BORDAU 2 stn DW 1554). The radular teeth are all similar in shape and size (Fig. 4I). The teeth have a narrow and elongate base and 3-4 pointed cusps.

REMARKS. — Habe (1952a) described Obrussena moeshimaensis as a species different from Obrussa bracteata . According to him, O. bracteata has a much higher spire and more whorls than O. moeshimaensis . However, these differences are probably related to the size of the specimens examined. The holotype of O. moeshimaensis is 2.7 mm long and has 3 whorls, whereas a syntype of O. bracteata is 5 mm long and has 3 whorls. A similar variation in the number of whorls with shell length has been observed in the material here examined. There are no consistent differences between O. bracteata and O. moeshimaensis to sustain the maintenance of two distinct species.

FIG. 5. Collection localities of species of Crenilabium Cossmann, 1889 , Obrussena Iredale, 1930 and Rictaxis Dall, 1871 in the southwest Pacific: σ, Crenilabium pacificus Kuroda & Habe, 1958 . Z, Obrussena bracteata (Iredale, 1925) . °, Rictaxis sanguinea n. sp.